1. Field of the Invention
The present invention relates generally to processes for forming composite beams and configurations of such beams, and more particularly to a process for continuously forming composite beam structures of predetermined cross-sectional shapes.
2. Description of Related Art
The use of pultrusion methods to effect the continuous production of structural members of constant cross-sectional configuration is well-known. Conventional pultrusion processes involve drawing a bundle of reinforcing material, such as glass filaments or fibers, from a source, wetting the fibers and impregnating them with a resin, as for example passing them through a bath in a reservoir, pulling the resin-impregnated fibers through a shaping die to align the fibers and manipulate the bundle to a desired cross-sectional configuration, and then curing the fibers in a mold while maintaining tension on the filaments. Because the fibers progress completely through the pultrusion process without being cut or chopped, the resulting products have exceptionally high longitudinal strength. Examples of processes of this type are disclosed in U.S. Pat. No. 3,793,108 to Goldsworthy, U.S. Pat. No. 4,394,338 to Fuway, U.S. Pat. No. 4,445,957 to Harvey, and U.S. Pat. No. 5,174,844 to Tong.
Articles that are produced by the pultrusion process include tool handles, mine shaft bolts, pipes, tubing, channel beams, fishing rods, etc. Of particular interest in this application are structural members.
U.S. Pat. No. 5,264,170 to Strachan discloses a system of manufacturing pultruded elements having a skin resin-bonded to a core, the elements preferably being tubular and having internal and external skins resin-bonded to the core. The process disclosed by Strachan comprises separately feeding core-forming materials and skin-forming materials along substantially vertical pathways to the inlet of a pultrulsion die station. The external and internal cross-sectional configuration of the elements is determined by the dies at the die station. External and internal skins are secured over the element to yield a tubular element.
It is also known in this technology that the size of pultruded parts is limited due to the high pull forces required to keep the materials moving through the die. There is no known method for producing lightweight composite beams without costly and time consuming secondary joining processes.
Against this background of known technology, the inventors have developed a process for the automated, continuous, formation of lightweight, composite structural elements which are structurally efficient and of superior quality.